SANTA CLARA, Calif. (AP) The 49ers aren't anointing Reuben Foster their next starting linebacker right away, but they did offer the recent first-round pick a vote of confidence Monday.

Foster received reps with the starters in practice next to NaVorro Bowman on Monday, minutes after San Francisco placed Malcolm Smith on injured reserve with a torn pectoral muscle. Smith is scheduled for surgery and will likely miss the season.

Foster will make his pro debut during Friday's preseason opener at Kansas City. Defensive coordinator Robert Saleh said Ray-Ray Armstrong will also get a chance to win the starting job at weak side linebacker.

"He needs reps. He's still a rookie," Saleh said of Foster. "The game is faster, the linemen are faster, they're stronger. The scheme is different. So, he just needs reps, over and over and over again. He just needs to get attacked, and all the different fundamentals that we're asking him to do, he needs to get attacked in those situations just so he understands what his weaknesses are within the scheme."

Foster was once considered a top-10 prospect, but he fell to the 31st pick in the draft after having surgery to repair a torn rotator cuff in his right shoulder. There were also questions about his behavior off the field after Foster was sent home from the scouting combine for an altercation with a hospital employee while waiting for his physical.

The former Alabama star missed the 49ers' offseason activities while recovering from the surgery and didn't appear in team drills until the start of training camp. During the first week of camp, he made three interceptions during 11-on-11 sessions and recovered a fumble while working with the reserves.

Coaches have been impressed by Foster's preparation in the film room. His knowledge of Saleh's new-look 4-3 defense allowed him to call the defense as the "mike" linebacker with the reserves during drills.

"You can't make one mistake twice," Foster said. "You got to learn from your mistake . but don't focus on that mistake (so) you mess up on something else."

Smith was on the practice field Monday helping his teammates with his left arm in a sling. His knowledge of the scheme is unique to the roster. He was named Super Bowl MVP with Seattle after the 2013 season while running a similar scheme, with Saleh working as an assistant on the staff.

"I don't hurt as much for the organization as I do for him and all the hard work he put in this offseason to position himself to have the best year of his career," Saleh said. "For that to happen to him when it happened to him, I feel sick for him."

Smith was signed to a five-year contract, presumably to start next to Bowman and ease the transition to Saleh's defense. But it was clear San Francisco viewed Foster as a potential starter when new general manager John Lynch traded back in Round 1 to take the Butkus Award winner.

"He's had flash plays and he's had busts that a common person won't notice," said Saleh. "What's great about him is that when he sees it once, he's good. So, even if he's made a mistake he'll be able to recoup, regather himself back up."